Stop using init-only setter for netstandard

src/Microsoft.FeatureManagement/ConfigurationFeatureDefinitionProvider.cs

@@ -58,12 +58,12 @@ public ConfigurationFeatureDefinitionProvider(IConfiguration configuration)
         /// <summary>
         /// The option that controls the behavior when "FeatureManagement" section in the configuration is missing.
         /// </summary>
-        public bool RootConfigurationFallbackEnabled { get; init; }
+        public bool RootConfigurationFallbackEnabled { get; set; }
 
         /// <summary>
         /// The logger for the configuration feature definition provider.
         /// </summary>
-        public ILogger Logger { get; init; }
+        public ILogger Logger { get; set; }
 
         /// <summary>
         /// Disposes the change subscription of the configuration.

src/Microsoft.FeatureManagement/FeatureFilters/TimeWindowFilter.cs

@@ -34,12 +34,12 @@ public TimeWindowFilter(ILoggerFactory loggerFactory = null)
         /// <summary>
         /// The application memory cache to store the start time of the closest active time window. By caching this time, the time window can minimize redundant computations when evaluating recurrence.
         /// </summary>
-        public IMemoryCache Cache { get; init; }
+        public IMemoryCache Cache { get; set; }
 
         /// <summary>
         /// This property allows the time window filter in our test suite to use simulated time.
         /// </summary>
-        internal ISystemClock SystemClock { get; init; }
+        internal ISystemClock SystemClock { get; set; }
 
         /// <summary>
         /// Binds configuration representing filter parameters to <see cref="TimeWindowFilterSettings"/>.

src/Microsoft.FeatureManagement/FeatureManager.cs

@@ -21,11 +21,11 @@ public sealed class FeatureManager : IFeatureManager
         private readonly TimeSpan ParametersCacheAbsoluteExpirationRelativeToNow = TimeSpan.FromDays(1);
 
         private readonly IFeatureDefinitionProvider _featureDefinitionProvider;
-        private readonly IEnumerable<IFeatureFilterMetadata> _featureFilters;
-        private readonly IEnumerable<ISessionManager> _sessionManagers;
         private readonly ConcurrentDictionary<string, IFeatureFilterMetadata> _filterMetadataCache;
         private readonly ConcurrentDictionary<string, ContextualFeatureFilterEvaluator> _contextualFeatureFilterCache;
         private readonly FeatureManagementOptions _options;
+        private IEnumerable<IFeatureFilterMetadata> _featureFilters;
+        private IEnumerable<ISessionManager> _sessionManagers;
 
         private class ConfigurationCacheItem
         {
@@ -60,7 +60,7 @@ public IEnumerable<IFeatureFilterMetadata> FeatureFilters
         {
             get => _featureFilters;
 
-            init
+            set
             {
                 _featureFilters = value ?? throw new ArgumentNullException(nameof(value));
             }
@@ -74,7 +74,7 @@ public IEnumerable<ISessionManager> SessionManagers
         {
             get => _sessionManagers;
 
-            init
+            set
             {
                 _sessionManagers = value ?? throw new ArgumentNullException(nameof(value));
             }
@@ -83,12 +83,12 @@ public IEnumerable<ISessionManager> SessionManagers
         /// <summary>
         /// The application memory cache to store feature filter settings.
         /// </summary>
-        public IMemoryCache Cache { get; init; }
+        public IMemoryCache Cache { get; set; }
 
         /// <summary>
         /// The logger for the feature manager.
         /// </summary>
-        public ILogger Logger { get; init; }
+        public ILogger Logger { get; set; }
 
         /// <summary>
         /// Checks whether a given feature is enabled.

src/Microsoft.FeatureManagement/Microsoft.FeatureManagement.csproj

@@ -15,7 +15,8 @@
     <SignAssembly>true</SignAssembly>
     <DelaySign>false</DelaySign>
     <AssemblyOriginatorKeyFile>..\..\build\Microsoft.FeatureManagement.snk</AssemblyOriginatorKeyFile>
-    <LangVersion>9.0</LangVersion>
+    <!-- Microsoft.FeatureManagement uses the feature of async streams which is not supported in versions of C# earlier than 8.0. -->
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>
 
   <PropertyGroup>